Femap 9.0 Makes the Right Moves in a New Direction

The faithful will find the updated interface no problem while new users find it opens doors to powerful analyses.

As a long-time user firing up v9.0 was something like switching from black and white to color TV (see Figure 1, below). After poking around the new interface warily, I soon learned that Femap’s developers didn’t take away my tried and true ways of working but provided an alternative interface that is consistent with that popularized by many MCAD-integrated analysis tools. New Femap users will find the Model Info tree and Entity Editor fast and convenient for setting up and querying both the simplest solid automeshed parts and the most complex mixed mesh plate and beam assemblies. Old hands will find everything they are used to, almost in the same place, while growing accustomed to the more graphical mode of data control.

Figure 1: The new Femap Version 9.0 interface. Click on image to enlarge.

Parasolid-Based Geometry Tools

Femap v9.0 has direct import/export translators for more than 25 FE (finite element) structural and CFD (computational fluid dynamics) solvers. It handles the database conversion, so you don’t need to know all the intricacies of file formats or construct templates. This lets you maintain a common FE database for projects involving multiple solving environments and, as an added benefit, it lets you swap out solvers as your needs change without making you relearn the model building and post-processing tool.

Femap’s approach to geometry support is similarly robust. Despite the buzz for keeping analysis and MCAD geometry common, most serious analyses involve geometry created specifically for simulation or models disassociated from the MCAD database and modified by the analyst for performance-verification process efficiency. Acknowledging this, Femap provides direct MCAD interfaces to CATIA, Pro/Engineer, and NX as well as neutral and kernel-based formats such as ACIS, IGES, Parasolid, and STEP.

I rarely have problems importing geometry from a variety of sources. If I do, Femap’s geometry healing and manipulation tools provide a reliable workaround. Femap’s integrated Parasolid modeling engine, an interesting and beneficial incorporation for a pure FE tool, has many MCAD-like capabilities, but it is not a MCAD tool. Access to solids feature history and some geometry parametrics would be a nice addition. But once you know what Femap’s geometry limits, this is seldom a hindrance.

The geometry tools are best used to subdivide a model for meshing, adding or removing simple features, or fixing imported databases. The geometry modeling tools are uniquely powerful for developing and modifying surfaces for weldments, including weld interface surfaces (see Figure 2, below) Femap’s mid-surface extraction tools, which have no restrictions on model construction techniques, are great for this as well. Where I once created models of weldments with only elements and nodes by extruding a mesh, I’m now spoiled by ready access to the underlying geometry in nearly all cases thanks to improvements in Femap’s geometry tools.

Figure 2: Femap 9’s assembly modeling and validation has been greatly enhanced. Click image to enlarge.

Meshing Tools

When an MCAD model imports with corrupted or missing surfaces, Femap provides an alternate means of getting the job done. Having options and workarounds with a problem mesh is more valuable than a tool that can mesh some parts faster some of the time.

With automatic tetrahedral meshing of a solid part, Femap typically fills a volume with elements as fast as any software around. However, where very thin or small features can confound an automesher, Femap provides several additional options. The problem surfaces or edges are identified by ID number and can be found graphically. You can correct these in the original MCAD database or use Femap’s geometry tools.

Femap has tools to group adjacent surfaces into a single analytical, or Boundary, surface for meshing. This can greatly reduce model size and improve mesh integrity. Using feature suppression, you can instruct the mesher to ignore problem areas. If all these options fail to generate the desired results, you can hand-stitch a surface mesh over the areas that won’t mesh automatically and direct Femap to fill the surface mesh with tetrahedrons. I don’t know the number of times I’ve relied on these tools to complete a project that otherwise would have dead-ended due to meshing problems.

This just scratches the surface of the Femap’s FE modeling capabilities. It supports a full suite of element types with customizable formulations for the various solvers it supports—just one menu away from the top-level control. The ability to use a geometric template for your model and still stitch in elements using semi-automatic or manual methods ensures that you maintain control of your model and aren’t limited in your ability to build the right mesh, not just the mesh that works with your MCAD.

FE Model Data Management Aids Validation

With multiple methods to construct a model, bookkeeping is important, especially if you hope to use a model for multiple load cases or test conditions and explore alternate geometric configurations. Femap’s Grouping and Layering capabilities aid this task by letting you generate an infinite number of named configurations for building and checking a model during construction and then querying the results when the solve is complete. These tools become extremely important with assemblies having multiple materials, element types, and element properties (materials, shell thicknesses, beam cross-sections, etc.). Femap can automatically build groups that contain elements with any given characteristic for model validation. An example might be to group all elements with common material properties. By toggling through the visibility of each material group, you can immediately and visually determine if material assignations were made correctly.

It is in model validation, the “bookkeeping” phase, that many complex analyses run into problems that wouldn’t necessarily be apparent when looking at the results. The old adage, “Measure twice, cut once” has applicability in FE modeling since many users rarely look back when they have results in front of them.

Figure 3: The Model Info tree

While Femap has always had good tools for this, using colors, Groups, and Layers to aid in property differentiation, v9.0 takes this a step further. The new Model Info tree as shown in Figure 3 (right) provides rapid access to all the important building blocks of a FE model, much like a Feature Tree in an MCAD tool. By expanding and collapsing branches of the tree, you toggle through all the properties and materials, as well as check the numeric input for each with a glance at the Entity Editor, also new in v9.0 (see Figure 4,below)

Once the inputs are confirmed, the Model Info tree lets you quickly highlight the elements that share each property or material to make sure they were assigned correctly. I’ve seen many analysts trip up by accidentally mistyping Young’s Modulus, density, or shell thickness when they could have caught the mistake with a last minute glance at the definition form. Some other useful features of the Entity Editor include context-sensitive help in a window just below the Editor that describes the meaning and/or importance of each selectable in the Editor form. The Entity Editor also displays the shape quality data on any selected element.

Figure 4: The Entity Editor window.

These new features should make it much easier to perform important model checks. V9.0 is the first pass at this functionality, and it represents a major rework of the Femap interfaces. However, in using the Model Info tree and Entity Editor, some suggestions for v9.1 come to mind. Adding a “visibility” attribute to the Model Info tree options would be a great enhancement. Simply right-mouse clicking a property and having the ability to make elements with that property invisible or make only elements with that property visible could speed up many model validation tasks. In the Loads and Constraints branches, current functionality allows only the creation, modification, or activation of Load Sets or Constraint Sets. Adding a shortcut to actual boundary condition creation to the tree would be an intuitive and helpful improvement. All in all though, a good start in a great direction for Femap.

Interactive Model Documentation

Model documentation is an important model validation task often overlooked. A well-organized and prepared report can highlight holes in the data or flaws in the model building logic. Many designer-oriented FEA tools have incorporated automatic or semi-automatic report generation tools that satisfy documentation needs, but these tools do not provide the interactive model validation benefits of constructing a report manually. Femap v9.0 takes a novel approach at a middle ground.

The ever-present Message Window in Femap has always been a place to view results of a model query. In v9.0, Message Window can be an interactive report generator if you want. All model data in this window is part of an editable document that you can cut from and paste into as well as save in RTF format. You can also annotate a model with running commentary. Consequently, you can construct a report by accessing normal Femap model validation functionality such as List Properties to generate a list of all the property definition data on the various element idealizations in the model; List Materials to report the material properties used; Check Sum Forces to report the load balance in the model; or List Output for a summary of the important output data in pre-determined or user-defined formats.

Femap v9.0 also incorporates a Data Table feature that lets you capture much of a model’s property or output data in a spreadsheet-like format that can be sorted and analyzed as needed to better understand trends or anomalies.

Editable Message Window and Data Table are so novel that their true utility probably won’t be realized until they are put through their paces on real projects. However, the flexibility they provide for model documentation and validation is obvious. The Model Info tree and Entity Editor are welcome additions, as they resemble proven methodologies in other tools. V9.0 also includes other new features that make navigating the interface easier, such as customizable icons and toolbars and the ability to keep multiple models open with tabbed windows.

Moving in a New Direction

Historically, the Femap team has aggressively optimized new functionality, so we should see this new direction come to maturity in a point release or two. If you are a Femap user, I recommend upgrading to v9.0 as soon as possible. If you have not yet tried Femap but are interested in taking your analysis to the next level, download a free trial license and see for yourself how Femap can become an indispensable tool in your performance simulation program.

Vince Adams is the Director of Analysis Services for IMPACT Engineering Solutions in Gurnee, Illinois. Send your feedback on this article via e-mail to [email protected]